Journal of Cancer Research and Therapeutics

REVIEW ARTICLE
Year
: 2015  |  Volume : 11  |  Issue : 3  |  Page : 545--548

Imaging findings after radiotherapy to the pelvis


Pavan Kumar Lachi1, Sujatha Patnaik2, K Amit2, K. V. J. R. Naidu1,  
1 Department of Radiation Oncology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
2 Department of Imaging and Radiology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India

Correspondence Address:
Pavan Kumar Lachi
NIMS, Hyderabad, Telangana
India

Abstract

Carcinoma cervix is the second most common malignancy in women worldwide, and it remains a leading cause of cancer-related death in women in developing countries. The use of radiation therapy to treat cancer inevitably involves exposure of normal tissues. As a result, patients may experience symptoms associated with damage to normal tissue during the course of therapy for a few weeks after therapy or months or years later. Here we describe few cases developed normal tissue complications following radiotherapy to the pelvis. Many factors contribute to risk and severity of normal tissue reactions; these factors are site specific and vary with time after treatment. Treatments that reduce the risk or severity of damage to normal tissue or that facilitate the healing of radiation injury are being developed. These could greatly improve the quality of life of patients treated for cancer.



How to cite this article:
Lachi PK, Patnaik S, Amit K, Naidu K. Imaging findings after radiotherapy to the pelvis.J Can Res Ther 2015;11:545-548


How to cite this URL:
Lachi PK, Patnaik S, Amit K, Naidu K. Imaging findings after radiotherapy to the pelvis. J Can Res Ther [serial online] 2015 [cited 2022 Aug 16 ];11:545-548
Available from: https://www.cancerjournal.net/text.asp?2015/11/3/545/160911


Full Text

 INTRODUCTION



Carcinoma cervix is the second most common malignancy in women worldwide, and it remains a leading cause of cancer-related death in women in developing countries. [1] Radiotherapy is the primary treatment modality for some pelvic malignancies, particularly cervical cancer. Radiotherapy is used along with chemotherapy for the locally advanced carcinoma cervix.

Complications related to radiation therapy are uncommon.

In the past two decades, a decrease in complications has been seen due to improvements in therapy, although the exact incidence of lower urinary tract dysfunction is unknown. [2]

However, because of the number of patients treated and the relatively long latency period for radiation injury, the ability to recognize characteristic radiation-induced pelvic tissue changes on follow-up images is important. These changes include bone and soft-tissue injury as well as gastrointestinal and genitourinary tract injury. Neurologic and vascular injuries after radiation are rare because of the relative radioresistance of these structures. Here, we describe some common and some unusual changes following pelvic radiation therapy.

Imaging of the female pelvis following chemotherapy and radiation therapy are particularly challenging due to alteration of the normal anatomy and loss of tissue planes. Radiologists should be familiar with both the expected posttreatment imaging findings and the imaging features of common complications to help make the correct interpretation and avoid possible pitfalls. [3]

 RADIOTHERAPY TECHNIQUE



Radiotherapy will have two components includes external beam radiotherapy (EBRT) and brachytherapy along with concurrent chemotherapy.

External beam radiotherapy will be given up to 50 Gy in 25 fractions 2 Gy per fraction. EBRT field arrangement [Figure 1]:

The superior border is set at the L4-5 interspace to encompass common iliac lymph nodesThe inferior border is set below the obturator foramen or 3 cm inferior to distal disease, whichever is lowerThe lateral border of the anteroposterior or posteroanterior field is set at 1.5-2 cm lateral to the pelvic brim with sparing of the medial aspect of the femoral headsThe anterior border of the lateral field is set anterior to the pubic symphysis with small-bowel blockThe posterior border of the lateral field is set posterior to the sacrum.{Figure 1}

Brachytherapy is either high dose rate brachytherapy 7 Gy per fraction, 3 fractions to a total dose of 21 Gy or low dose rate brachytherapy 20-25 Gy single fraction.

 GENITOURINARY CHANGES



Injuries to the urinary tract are seen more frequently 3-5 years after treatment. The overall incidence of urologic complications after pelvic irradiation is reported to be approximately 0.5-3%.

However, in a series reported by Dean and Lytton [4] showed 2.5% of such complications could be ascribed to the effects of radiation alone. They found that the development of urologic complications was related to the radiation dosage and previous bladder operations. The incidence of radiation cystitis is reported to range from 3% to 12%, again depending on the dose to the bladder [Figure 2]. The risk of ureteral stenosis in cervical cancer is 1.0%, 1.2%, 2.2%, and 2.5% at 5, 10, 15, and 20 years, respectively. [5] Ureteral injury may not become apparent for many years after therapy, and, therefore, continued surveillance of renal function in these patients is necessary [Figure 3].{Figure 2}{Figure 3}

 GASTROINTESTINAL CHANGES



Injury to the gastrointestinal tract usually appears within the first 2 years after radiation therapy. The overall incidence of chronic radiation injury to the bowel after radiotherapy to the pelvis is about 1-5%. [6] The most important risk factor for injury to the gastrointestinal tract is the received dose of radiation. Rapidly proliferating cells, such as those in the mucosa of the small intestine, are most radiosensitive and, therefore, at highest risk for acute injury, which occurs within weeks of therapy and is rarely studied radiographically. The changes in the vascular and interstitial connective tissues are more insidious, and the initial injury leads to progressive ischemia of the intestinal wall. Chronic radiation enteritis may develop months or years after therapy, and imaging does play a role in the evaluation of these patients.

The ileum is the most frequently injured segment of the small intestine because of its location in the pelvis. Submucosal edema and fibrosis are seen at barium examinations as thickening and straightening of small-bowel folds and separation of adjacent loops. Computed tomography (CT) can directly reveal bowel wall thickening related to submucosal edema [Figure 4]a and b. Fluoroscopic evaluation may show single or multiple areas of stenosis and small-bowel obstruction. Altered peristalsis may also be encountered. Fibrotic changes in the mesentery may cause fixation of bowel loops; in this condition, the loops appear angulated, and tethered at small-bowel follow through examination. Increased density in the mesentery may be evident at CT. Radiation damage to the colon can also be shown radiographically. Loss of distensibility with strictures of various lengths and degrees of narrowing may be encountered. Widening of the presacral space may also be seen [Figure 5].{Figure 4}{Figure 5}

Barium studies may show mucosal changes such as ulceration, pseudopolypoid protrusions, or contour irregularities ranging from tiny serrations to ragged margins and even circumferential lesions simulating malignancy [Figure 6]. Complex fistulas may also develop [Figure 7] and [Figure 8]. The rectum is relatively radioresistant, but is involved most commonly because of its fixed location near organs in the pelvis that are frequently targeted for radiotherapy.{Figure 6}{Figure 7}{Figure 8}

 Bone and Soft Tissue Changes



Radiation also affects bone cells and vessels by leaving an acellular, ischemic frame that on radiographs initially appears to be normal structure. The median time from the end of radiotherapy to the diagnosis of pelvic bone complications or changes was 25 months (range 2-45 months). The 1, 2, and 3 years cumulative incidences were 22%, 41%, and 49%, respectively. [7]

Small lytic areas in irradiated bone may be difficult to distinguish from metastatic disease. As ischemic changes progress, the bone is more likely to fracture. Healing of irradiated bone is also abnormal. Spontaneous fractures, nonunion of fractures, aseptic necrosis, and bone resorption may occur [Figure 9]. Insufficiency fractures are frequently encountered in the sacrum, and patients present with pain that may be clinically indistinguishable from pain related to tumor recurrence.{Figure 9}

Soft-tissue changes in the pelvis include thickening of the perirectal fascia and presacral fibrous tissue. Such changes should stabilize approximately 12 weeks after completion of therapy. [8] Secondary malignancy in irradiated tissues is rare, with a reported incidence of 0.1%. Sarcomas may be of soft-tissue or bony origin. The latency period for development of radiation-induced malignancy is long, typically 10 years or more.

 CONCLUSION



Radiation therapy is the treatment of choice for the locally advanced carcinoma cervix.

Late complications due to radiotherapy are the following:

Genitor urinary complications such as ureteral stricture and cystitisGasto intestinal complications such as enteritis, strictures, and fistulaeMusculoskeletal complications such as osteitis, osteolysis, and osteoporosis.

Imaging plays an important role in the diagnosis of these complications.

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